So here is my query from Carolina Garden Web, the forum that solved my Japanese Knotweed mystery:
What has kept me from throwing this thing away is a new clue that I uncovered over the weekend..... Mine may be a less-than invasive version that blooms red in the late summer. To be safe, I will contain it inside of a large pot (possibly an old recycled trash can- Oscar the Grouch style). I remember my neighbor said it was a red bloomer. The roadside pest has flowers of white. And his mature clumps look tame. Tall....but tame.
P.S., another common name for this plant, besides "Mexican bamboo," is "kiss me over the garden gate." Hmmm. I don't think I am ready for that.